Patent GB-191212547-A (GB)
Title: Telephone Exchange Systems.
Inventor: CORWIN ELMER REED
IPC: H04M3/523
Filed: 1912-05-28
Granted: 1913-05-28
Abstract: 12,547. Corwin, E. R. May 28. Semi-automatic exchange systems in which each line is provided with a selector for connecting it to an idle operator are arranged so that the operator can make plug connexions between two subscribers independent of the selecting-apparatus. When subscriber 120 raises his receiver, a circuit is completed from the battery 19 over the interrupter 18, the winding 14 of the selector magnet of the line 120, the two parts of the line 120, to earth at 24. The magnet 14 rotates the selector until the arms 12, 12<1>, 12<2> reach the contacts 13, 13<1>, 13<2> of an idle operator, when a circuit is closed from ground at 27, over contacts 28, 13, 12, magnet 21, contact 25, which is closed at the first movement of the selector, and battery 19. The magnet 21 completes a hold-on circuit for itself and breaks the circuit of the winding 14 over the contact 20. The selector contacts are thus held in this position, and the operator's call signal 8 is energized by' a circuit from the battery 19 over the signal 8, the contacts 13<1>, 12<1>, the contact 33, the line 120 to earth at 24. The operator's speaking set 32 is now connected over the contacts 13<1>, 13<2>, and the contacts of the relay 21 to the calling line. The armature 30 of the magnet 8, by removing the ground connexion from the lead of the contacts 13, renders this operator busy for other calls. The operator's position can also be made busy by a hand switch 28 or by the insertion of a plug 7 in a jack 6, a circuit being then completed from ground at the magnet 23 over the jack and plug, the magnet 34<3>, and the battery 19. The armature of the magnet 34<3> completes a circuit for the magnet 29 over the magnet 35 and the contacts of the armatures of the magnets 34<3> to the battery 19. The magnet 29 makes the position busy by disconnecting the earth 27, but the magnet 29 is de-energized when the second plug is inserted and the second magnet 34<3> is energized. The energizing of the magnet 23 completes a circuit for the selector release winding 36 over the contact 37, the contact 25, and the battery 19. The selector is thus released as soon as the answering plug is inserted in the jack. The operator's speaking set is included in a cord-circuit connected to a calling line by the armature of the magnet 35. The phonograph 38 may be used for giving the number of the calling subscriber to the operator. The operator makes a busy test through the magnet b and transformer c when the jack 26 is touched by the tip of the plug. When the calling plug is inserted, the magnet 34<3> attracts its armatures 40, 41, and the ringing-circuit is completed from the generator 44 over the armature 41, right-hand armature of magnet d, ring of plug, bell 4, tip of plug, left-hand armature of magnet d to earth. If the calling subscriber hangs up his receiver before the called subscriber answers, a circuit is made from ground at relay 24 through tip of plug of calling subscriber, contact of relay a, which is now de-energized, and right-hand winding of relay d, to battery. The attraction of the right-hand armature of relay d cuts off the ringing current from the called subscriber's line.